1. Field of the Invention
The present invention relates to the field of power electronics, and particularly to a method for transmitting data and a wireless charger for implementing the same.
2. Description of the Related Art
Wireless charging has been widely applied in the field of electronic products, particularly low power electronic products, e.g., mobile phones, MP3 players, digital cameras, portable computers, etc., due to its convenience and practicality. A wireless charger in the prior art typically comprises a transformer composed of primary winding L1 and secondary winding L2, and the wireless charger typically transmits power from a transmitter to a receiver through coupling over a magnetic field between the primary and secondary windings of the transformer. Along with rapid development of wireless charging, how to communicate data wirelessly over the same wireless charger has become a current hot issue under investigation, and an existing solution is typically to modulate the amplitude of current or voltage on an inductive element of a data signal transmitter and to transmit data, and through coupling over a magnetic field, a data signal receiver demodulates the inductive signal on an inductive element into the data signal transmitted thereto, so that the data communication is achieved by the wireless charger.
In the above-mentioned data transmission process, variation ΔI in amplitude of the current on the inductive element has a considerable influence upon the demodulation, and as illustrated in FIG. 1, there is a significant variation ΔIH in amplitude of the current on the inductive element (e.g., the primary and secondary windings of the transformer) at moment t1 so that the signal is easy to demodulate, whereas the output current of the wireless charger is lower at moment t3 with lower driving current after charging for a long period of time and accordingly there is a lower variation ΔIL in amplitude of the current on the inductive element so that the signal is difficult to demodulate at the data receiver. When the load current is initially low as represented by waveform I′ in FIG. 1, variation ΔIH in amplitude of the current on the inductive element is at a very low level at moment t1, and the data signal is difficult to demodulate at the data receiver; and variation ΔIL in amplitude of the current on the inductive element has become almost absent at moment t3 so that the demodulation may be failed at the data receiver, and consequently, a more sophisticated and expensive circuit has to be implemented for the demodulation.